The field of the invention are dyes for marking hydrocarbon compositions. More particularly, the invention relates to non-mutagenic dyes for marking hydrocarbon compositions. Dyes have often been used to color petroleum products such as diesel fuel, gasoline, lubricating oils, grease, automatic transmission fluids and plastic products. Red is a particularly important petroleum dye color used in a variety of applications. Internal Revenue Service regulations, for instance, require the use of red dye to identify off-road diesel fuels. There is concern, however, that some red dyes presently used in the industry, particularly amino-azo benzene derived red dyes, pose potential health risks because they may be mutagenic or carcinogenic. Moreover, the manufacture of these materials requires handling mutagenic, carcinogenic materials and intermediates. Handling these dyes or products containing the dyes, may involve some level of health risk because of the possible mutagenic character of the dye.
Red azo dyes for coloring petroleum products have been commercially available for many years. For example, U.S. Pat. Nos. 3,690,809 and 3,704,106 describe liquid dyes, some of which have been useful for coloring petroleum products, and, in some instances, plastics. Although these dyes may be effective colorants, the raw materials and intermediate products used in their production may present health risks if not handled properly. Some of the more widely used compounds, such as red C. I. Solvent Reds 24 and 164, are derived wholly or in part from 2-methylaniline, which is a suspected human carcinogen. In particular, to produce the foregoing red dyes, 2-methylaniline is converted, in whole or in part, to 1-amino 2,2′ dimethyl-4-azobenzene, which is also known to be a carcinogen. The azobenzene compound, which is sometimes isolated, is then converted to a diazonium compound that is azo coupled to 2 naphthalenol, or an alkyl derivative thereof, to produce the red dye. The red dye is typically sold as a liquid concentrate, but may also be prepared and used as an unsolvated solid. In addition to potential health concerns associated with the final dye products and the precursor these conventional red azo dyes are somewhat unstable in that they can be degraded under conditions of excessive heat or by contact with a protogenic acid or chemical reducing agent. During degradation, for instance, Solvent Reds 24 and 164 produce 1-amino-2,2′-dimethyl-4-azobenzene and/or its homologues, which are also suspected to have carcinogenic activity.
U.S. Pat. No. 5,676,708 (“the '708 Patent”) discloses diaazo dyes having a highly unpredictable level of mutagenicity. For example, 2,2′-dimethylaminoazobenzene derivatives produced in Example 1 exhibited strong mutagenic response under the “Ames Test”. On the other hand, a 2,2′-diethylaminoazobenzene derivative produced in Example 2 and a 2-2′-di(1-methylethyl)aminoazobenzene derivative produced in Example 6 using the same process used in Example 1 showed no positive mutagenic response using the same Ames Test. To put this in perspective, simply changing two R2 groups from methyl to ethyl or isopropyl completely eliminated strong mutagenicity in the dyes of the '708 Patent.
The azo dyes from the '708 Patent are configured in an “ortho-ortho” configuration (i.e., the R1 groups for Formula I of the '708 Patent are in ortho positions). Generally speaking, it is expected that diazo dyes having a “meta-meta” configuration (i.e., if the R groups for Formula I of the '708 Patent were in meta positions) would be mutagenic like their ortho-ortho counterparts and/or have lower color values than their ortho-ortho counterparts. In other words, meta-meta diazo dyes are considered inferior to their ortho-ortho counterparts. As such, relatively little attention has been paid to their development. Despite the ortho-ortho diazo dyes of the '708 Patent being described in an issued patent in 1997, the inventors of the present disclosure are not aware of any pursuit of meta-meta diazo dyes. This is suspected to be a result of a person of ordinary skill in the art believing that meta-meta diazo dyes having similar substitutions as the ortho-ortho diazo dyes of the '708 Patent would have similar mutagenicity, lower color value, or both.
Producing dyes and compositions which present lower carcinogenic risks is a desirable goal which can lower health risks for dye manufacturers and consumers. Unlike the mutagenic Solvent Red 164 currently known, the molecule and/or dye component and/or composition presently disclosed yields a negative Ames test indicating that the dyes are non-mutagenic, while having comparable properties (color strength, shade, stability, etc) to the mutagenic Solvent Red 164. The starting materials, intermediates, and degradation products of the present invention, also present reduced mutagenic risks.